1. Field of the Invention
This invention relates to a print head device which includes a print head unit carrying a print head thereon, and an ink cartridge mounted in the print head unit, and an ink jet printer incorporating the print head unit, more particularly an ink jet printer of this kind which uses a tape as a medium to be printed upon.
2. Prior Art
Conventionally, an ink jet printer of this kind includes a type in which an ink delivery port of an ink cartridge is tightly connected to a connecting cap (connecting member) of a print head unit thereof in surface-to-surface contact. In the ink jet printer of this type, a seal packing is interposed between the connecting cap and the ink delivery port such that the seal packing is fitted on the connecting cap, for preventing evaporation of a solvent contained in ink. When an ink cartridge is mounted in the print head unit, a distal end portion on an ink cartridge-side of the seal packing is deformed by. compression such that the distal end is expanded, and brought into annular intimate contact with a rim of the ink delivery port. This makes it possible to prevent vaporization of water content of the ink and leakage of the ink itself from the ink cartridge mounted in the print head unit.
In the conventional seal packing of the above-mentioned kind, the distal end portion of the seal packing is compressed and deformed such that the distal end is expanded, by the force applied in the mounting of the ink cartridge. However, if the distal end portion of the seal packing is brought into nonuniform surface-to-surface abutment with the rim of the ink delivery port, the distal end portion is deformed not into a proper annular shape but into a distorted annular shape, in plan view. In such a case, there is a fear that a gap is produced between the distal end portion of the seal packing and the rim of the ink delivery port. Further, in an ink cartridge containing a plurality of colors of inks for color printing, deformed distal end portions of seal packings for the respective ink delivery ports can be brought into contact with each other, thereby causing mixture of inks of different colors.
Further, the urging force of the ink cartridge required for deforming the seal packing by compression is increased in proportion to the amount of the deformation, so that when an ink cartridge for use in color printing is mounted, a very large urging force is required to simultaneously deform a plurality of seal packings, which can undesirably deform a supporting member, such as a carriage bar or the like, at which the urging force is finally received or withstood.
It is a first object of the invention to provide a print head device in which an ink cartridge can be mounted with a small mounting force without spoiling the sealing performance of a seal packing and minimizing the deformation of a contact portion of the seal packing where the ink cartridge is brought into contact.
It is a second object of the invention to provide an ink jet printer including a print head device in which an ink cartridge can be mounted with a small mounting force without spoiling the sealing performance of a seal packing and minimizing the deformation of a contact portion of the seal packing where the ink cartridge is brought into contact.
To attain the first object, according to a first aspect of the invention, there is provided a print head device comprising:
a print head unit, the print head unit having an ink jet print head, and an ink reception block for receiving supply of ink;
an ink cartridge, the ink cartridge being removably mounted in the print head unit, and having an ink delivery block for delivering ink therefrom; and
a seal packing having a generally hollow cylindrical shape and arranged between the ink delivery block of the ink cartridge and the ink reception block of the print head unit,
the seal packing having:
a fitting portion for airtight fit on a peripheral surface of the ink reception block;
an intimate contact portion for intimate contact with the ink delivery block; and
an intermediate hollow cylindrical portion continuous between the fitting portion and the intimate contact portion, and formed to be smaller in thickness than the fitting portion and the intimate contact portion.
According to this print head, the intermediate hollow cylindrical portion is formed to be smaller in thickness than the fitting portion and the contact portion, so that when an urging force acts axially on the seal packing in accordance with the mounting of the ink cartridge, the intermediate hollow cylindrical portion is preferentially deformed by compression. The deformation of the intermediate hollow cylindrical portion is controlled by the fitting portion and the contact portion. That is, the fitting portion and the contact portion are formed at opposite axial ends of the seal packing such that they have an increased thickness, and hence a stress responsive to the urging force applied to the seal packing is concentrated on the intermediate hollow cylindrical portion, which is expanded outwardly to be deformed such that the intermediate hollow cylindrical portion has an outwardly expanding arcuate profile in radial cross-section. Consequently, not only the fitting portion but also the intimate contact portion brought into intimate contact with the ink delivery block of the ink cartridge is prevented from being expanded and deformed before and after the ink cartridge is mounted. This also prevents the compression or contraction of the seal packing from causing displacement of the intimate contact portion from its proper contact position. Therefore, it is possible to enhance the sealing performance of the seal packing and component parts associated therewith as well as effectively prevent colors of inks from being undesirably mixed. Further, when the intermediate hollow cylindrical portion is deformed such that it has an outwardly expanding arcuate profile in radial cross-section, the direction of the urging force and that of the deformation are orthogonal to each other, so that the rate of increase in the stress (spring force) responsive to the urging force is progressively decreased with respect to the pressing stroke of the ink cartridge. Therefore, the mounting force required for mounting the ink cartridge can be held at a low level.
Preferably, the ink reception block has a peripheral surface formed with an annular groove, and the fitting portion has an inner peripheral surface formed with an annular projection for being fitted in the annular groove.
According to this preferred embodiment, the annular projection of the seal packing is fitted in the annular groove of the ink reception block, whereby the seal packing is immovably held, and the annular projection is brought into intimate contact with the annular groove such that the annular projection air tightly narrows the annular groove. This makes it possible to enhance the sealing performance of the fitting portion of the seal packing.
Preferably, the annular groove is arcuate in radial cross-sectional profile, and the annular projection has a shape arcuate in radial cross-sectional profile and complementary to the annular groove.
According to this preferred embodiment, the annular projection and the annular groove are in intimate contact with each other in a large contact area, thereby making it possible to further increase the sealing performance of the fitting portion of the seal packing.
Preferably, the seal packing has an inner peripheral surface which is axially flush and extends from the intermediate hollow cylindrical portion to the intimate contact portion, and the seal packing has an outer peripheral surface which is axially flush and extends from the intermediate hollow cylindrical portion to the fitting portion.
According to this preferred embodiment, when the seal packing is formed as a unitary member, it can be molded with ease by using an upper mold and a lower mold formed in view of die cutting.
Preferably, the intimate contact portion has an engagement portion for engagement with the ink cartridge, the engagement portion being arcuate in radial cross-sectional profile.
According to this preferred embodiment, the intimate contact portion can be in stable contact with the ink delivery block, thereby enhancing the sealing performance of the intimate contact portion of the seal packing.
Preferably, the ink cartridge is formed with a groove for engagement with at least one portion of the intimate contact portion.
According to this preferred embodiment, a contact position at which the intimate contact portion of the seal packing is brought into intimate contact with the ink delivery block can be prevented from being displaced when the ink cartridge is mounted.
More preferably, the at least one portion of the intimate contact portion is an engagement portion for engagement with the groove, the engagement portion being arcuate in radial cross-sectional profile.
To attain the second object, according to a second aspect of the invention, there is provided an ink jet printer including a print head device, the print head device comprising:
a print head unit, the print head unit having an ink jet print head, and an ink reception block for receiving supply of ink;
an ink cartridge, the ink cartridge being removably mounted in the print head unit, and having an ink delivery block for delivering the ink therefrom; and
a seal packing having a generally hollow cylindrical shape and arranged between the ink delivery block of the ink cartridge and the ink reception block of the print head unit,
the seal packing having:
a fitting portion for airtight fit on a peripheral surface of the ink reception block;
an intimate contact portion for intimate contact with the ink delivery block; and
an intermediate hollow cylindrical portion continuous between the fitting portion and the intimate contact portion, and formed to be smaller in thickness than the fitting portion and the intimate contact portion.
According to this ink jet printer, the ink cartridge can be mounted with a relatively small force without spoiling the sealing performance of the seal packing. Further, it is possible to effectively prevent mixture of color inks caused by mounting and removal of the ink cartridge and leakage of air from the seal packing. That is, it is possible to construct a user-friendly ink jet printer which is improved in reliability.
Preferably, the ink jet printer includes a tape cartridge containing a printing tape on which printing is carried out by the print head device, the tape cartridge being removably mounted in the ink jet printer.
The above and other objects, features, and advantages of the invention will become more apparent from the following detailed description taken in conjunction with the accompanying drawings.